1. Field of the Invention
This invention relates to an electronic musical instrument and especially to modification of a processing system which is applied when a musical tone to be generated is specified continuously or duplicately.
2. Description of the Prior Art
The musical tone which is generally generated by an electronic musical instrument has an envelope waveform as shown in FIG. 5. In FIG. 5 the arrow mark "a" indicates a key ON timing, the arrow mark "b" indicates a key OFF timing, 101 is an attack section, 102 is a fist decay section, 103 is a sustain section, 104 is a release section. Soon after a key is turned on, the attack section 101 and fast decay section 102 are formed. While key ON is kept, the sustain section 103 of constant level is formed. If a key is turned off, the release section 104 of decay waveform is formed, and the tone is cleared.
The general keyboard type electronic musical instrument has 8 to 16 sound sources. The number of musical tones which can be generated at the same time is equal to the number of a sound sources. When a key of keyboard is depressed, the control circuit assigns this sound successively to the sound sources waiting for tone generation so that a tone is generated. In the case when two or more keys are depressed simultaneously or when the sustain pedal is used, the number of tones to be generated may exceed the number of sound sources. In such a case the first generated musical tone is forcibly cleared and a new musical tone is generated. But if a musical tone being generated is cleared, a click-like noise unfavorable for musical tone occurs. Therefore, in the case when a musical tone being generated must be once cleared and then next new musical tone must be generated, the musical tone to be cleared is not cut off but rapidly decayed (force-damped) as shown in FIG. 5 (105) to clear it, and then the new musical tone is generated after a proper time interval. The arrow mark "c" in FIG. 5 indicates a key ON timing of the new musical tone, the arrow mark "d" indicates the tone generating timing of the new musical tone.
When a musical tone which must be cleared is being generated at high level, force-damp takes much time. When tone is generated at low level, the required time is short. The conventional force-damp control (i.e. Japanese patent publication Sho 63-7394) features that the new musical tone is generated after a specific waiting time irrespective of at which stage of attack section-release section the musical tone being generated exists. Therefore when the force-damp is applied to a musical tone which is going to be cleared in the release section, excessive pause occurs due to excessively long waiting time. In the case when the force-damp is applied to the musical tone in the sustain state at high level, the waiting time is too short as compared to the force-damp time, so that the next musical tone is generated before the previous tone is cleared.
To eliminate these defects, the tone generation level of the musical tone to be cleared must be judged, and a waiting time proportional to this tone generation level must be set. However, to provide a function of detecting the tone generation level of analog musical tone signal and of taking it as digital data in the conventional electronic musical instrument (synthesizer, etc.) which uses a CPU for tone generation control, a detecting circuit and an A/D converter circuit are additionally required, so that the circuit becomes complicated and cost rises.